1. Field of the Invention
The present invention relates to a positioning device and a method for simultaneously positioning a plurality of substrates, such as semiconductor wafers.
2. Description of the Related Art
During the process of fabricating a semiconductor device, a substrate conveyor and processing apparatus is widely used to convey a substrate to be processed, such as a semiconductor wafer or glass LCD (liquid crystal display) substrate, into a processing tank in which is stored a processing liquid such as a chemical or rinse (washing liquid) and then into a drying portion, to perform processes thereon such as washing and drying.
The description below concerns a substrate conveyor and processing apparatus that is an apparatus for washing and drying semiconductor wafers. In this type of apparatus, there is generally a line of a plurality of processing units and washing units for conveyor devices disposed between an inlet portion for carriers containing unprocessed wafers and an outlet portion for carriers containing processed wafers.
To wash a large number of wafers, such as about 50 wafers, efficiently in such a substrate conveyor and processing apparatus, the wafers are conveyed in a vertical orientation, which is a suitable method for conveying the wafers into and out of each of the processing units.
However, recent advances in higher levels of integration of smaller components and greater levels of mass-production have led to an increase in size of wafers from 8 inches to 12 inches. This increase in diameter of the wafers, together with the resultant increase in weight thereof, has raised a problem in that, if the wafers are conveyed within each carrier in the conventional vertical state, positional slipping will occur when the wafers are transferred between the inlet or outlet portion and the processing units, causing particles to be generated by the movement of the wafers and other parts, and thus reducing the fabrication yield.
As a result of intense research intended to solve this problem, the present inventors and applicants have developed a technique of conveying a plurality of wafers, such as 50 wafers, in a horizontal state then changing the attitude of those wafers to a vertical state before they are conveyed into the processing units.
When it comes to changing the attitude of a plurality of wafers from a horizontal state to a vertical state, it is necessary to position all of the wafers in order to align them. A positioning device in which a wafer is placed on a turntable and a notch in the wafer is detected by a sensor is known as means for positioning the wafers (refer to Japanese Patent Application Laid-Open No. 5-218179).
However, this method can only detect the position of a single wafer, During the simultaneous positioning of a plurality of wafers in a horizontal state, it is necessary to place all of the wafers with the centers of rotation thereof aligned, and detect the notches thereof under the same conditions. Therefore, if a conventional detection device is used therefor, the structure of the positioning device will become larger and more complicated, and also the task of positioning the wafers will become laborious.